In the fall, we all do our best to prepare our bees for the long winter months. We ensure they are healthy, have a large enough bee cluster, ample honey stores to get them through, and a hive that is ventilated, insulated and dry.
Bees that overwinter live almost entirely inside the hive. Bees usually only leave for cleansing flights on days when temperatures are above 14°C. It is risky leaving the hive on days less than this because their wings can freeze at 10°C, and they risk not making it back to the hive.
Bees begin to form a cluster inside a hive once temperatures are below 14°C. They form a cluster around the queen. As a colony, they overwinter in a cluster and move, eat and perform hive duties together. The worker bees take turns rotating from the inside core of the cluster to the outside. On the inside of the cluster, the bees continue to care for the queen.
The honey bees biggest job inside the hive during the winter months is to keep the queen warm. They do this by vibrating their flight muscles to create heat in the hive. The centre of a cluster can get up to 35ºC! While the exterior of the cluster can be around 9°C.
To manage the temperature of the cluster, the bees will contract or expand the cluster to increase or decrease the temperature. If the core temperatures need to increase, they will contract to limit the air flow. If the temperature needs to decrease, they loosen the cluster to increase the air flow and cool the core of the cluster.
Creating heat uses a lot of energy and requires a food source. The food they rely on in the winter months is the honey stores that are left in the hive. In cold climates bees require a lot more honey stores for the winter months. It is important that the honey stores are accessible to the bees as they must move together in a cluster. However, if the food source is too far away during a long duration of cold temperatures, they may not be able to get it. If they don't get a chance to loosen their cluster and regroup, it can be difficult for the bees to reach the food they need.
Check out this fun animation about what honey bees do during the winter months: https://youtu.be/aPj0W2eT9PM
Honey bees are one of the few insects that do not hibernate in winter. Overwintering bees live up to six months. Unlike summer bees who live only four to six weeks. The main reason overwintering bees live longer is that they do not rear brood. Another key difference is that winter bees mainly live inside the hive for the winter months. Summer bees live inside and outside the hive collecting pollen and nectar, rearing brood and making honey.
The cluster is made up entirely of female worker bees (and the queen). Drones (male bees) are kicked out of the hive as temperatures drop. Older bees usually stay on the outer part of the cluster and younger bees on the inside. If older bees die, they just leave or fall off the outer cluster.
We don’t want to disturb an overwintering hive too much, but on warmer days, you can take a peak inside to ensure there is honey stores and that it is accessible to the bees. Honey frames should be on both sides of the cluster and above the cluster in a Langstroth hive.
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